The embodiment relates to a wireless power receiver and a power control method thereof. A wireless power transmission or a wireless energy transfer refers to a technology of wirelessly transferring electric energy to desired devices. In the 1800's, an electric motor or a transformer employing the principle of electromagnetic induction has been extensively used and then a method for transmitting electrical energy by irradiating electromagnetic waves, such as radio waves or lasers, has been suggested. Actually, electrical toothbrushes or electrical razors, which are frequently used in daily life, are charged based on the principle of electromagnetic induction. The electromagnetic induction refers to a phenomenon in which voltage is induced so that current flows when a magnetic field is varied around a conductor. Although the commercialization of the electromagnetic induction technology has been rapidly progressed around small-size devices, the power transmission distance is short.
Until now, wireless energy transmission schemes include a remote telecommunication technology based on resonance and a short wave radio frequency in addition to the electromagnetic induction.
Recently, among wireless power transmitting technologies, an energy transmitting scheme employing electromagnetic induction or resonance has been widely used.
In a wireless power transmission system employing electromagnetic induction or resonance, since an electrical signal generated between the wireless power transmitter and the wireless power receiver is wirelessly transferred through coils, a user may easily charge electronic appliances such as a portable device.
As electric and electronic technology has been advanced and a battery has been used in modern times, power supply is carried out by using a battery in a wireless power transmission system.
However, in the related art, as the voltage applied to a battery is changed, the charged state of the battery is unstable.